Putting a final post script onto this topic, this weekend I finally did the last significant repair to the machine, a minor cosmetic repair, and one procedure with a thought to the future.

First, the last repair: yesterday I removed and replaced the broken Player 2 controller jack. As you can see in the second picture, one of the pins was broken clean off. Several others were bent and while straightening them, this one broke, necessitating the R&R. I used a cheap spring-loaded desoldering iron (about $17 on Amazon). It's only a 30 watt iron so it takes a few minutes to heat up to effective temperature but it works like charm. Basically one or two passes at each pin and they were free.

Having done the machine is now 100% functional in every respect, even 2-player games (something I haven't done in 30 years). But it needed to be done to call this restoration "complete."

The next procedure, today I decided to get rid of that now-unnecessary RF modulator. I've never tried to actually remove one before, though I've certainly disconnected them and cut them out of the video circuit before on this and other systems. So using a technique well-demonstrated on one of Jon's videos, I finally got this ugly, rusted irritant out of the way. Basically, heat the two lugs closest to the back of the board until the solder is nice and soft on both sides, then work a small screwdriver under the back edge and work those two lugs up and out as you move the iron to keep the solder on both lugs hot. I had to cut out the daughterboard at the back of the can to allow me to bend the thing back. Once the two back lugs were free, and with the daughterboard out of the way, I repeated the procedure at the two remaining lugs. I also removed the now-superfluous channel selector switch while I was at it. Look how much board real-estate I have now. Maybe someday I'll try to install a VBXE or something else in that space. Time will tell. The cheap desoldering iron took care of the switch in seconds, and the RF modulator daughterboard connections and the pin stubs in a few seconds more.

Last, and definitely least, I replaced the right rear rubber foot on the bottom case. It was hard, disintegrating and wearing away on one side as if it had been scraped with sandpaper or a file at some point. I scraped it out with a small flat screwdriver, cleaned the recess with alcohol and stuck on a new rubber foot.

In case anyone wants to see what I'm up to with the "Ugly Duckling," I made a short video.

tl;dr - I'm converting the board to use a single-chip OS from an 800XL in preparation for eventual installation of an Ultimate 1MB board.

Perhaps I'm missing something, but why go to all the trouble to change over to a 28 pin OS ROM and the later MMU when you plan to install a U1MB which would take over those functions anyway?

Edit: Just figured it out. because you need the OS ROM and the MMU configured the same as a later XL so that when you pull those chips the U1MB will be able to plug in their place and work. The U1MB depends upon having a 28 pin ROM socket with the appropriate signals.

Well, the 1200XL expects to find half of the 16K rom in each socket, despite the fact that so many 1200XL’s were built with 28-pin sockets. So to install the U1MB with one 28-pin OS connector, you rearrange the jumpers on the board and run the address line via the jumper wire from pin 23 of the CPU over to where W6 was located. At that point, the system OS addressing is just like an 800XL. In fact, you can go further and install a BASIC rom in the other socket but it requires a few more jumper wires.

So at this point, installing a U1MB is more or less the same as in any other XL machine. Installing the XL OS and MMU merely serves as a test to see if the board reconfiguration was successful. When it comes time to put the U1MB in there, both get removed of course.

This past week I received another Ultimate 1MB board from Lotharek which I had ordered two weeks back, so this weekend it was time to finish up this Ugly Duckling machine and make it my daily driver, finally!

With the work I did last month to configure the board for a single-chip OS, installation of the U1MB was pretty much a piece of cake. One or two technique points that are worth mentioning for people who've never done this kind of work before ... Installation of the U1MB requires running four wires from the U1MB to the board (or the shoulders of chips) to pick up four signals not otherwise picked up from the OS ROM socket or MMU socket - Phi2, Reset, R/W and Halt. Vias for all these signals are easy to reach but the one commonly used for Reset on the 1200XL is very, very close to a small axial capacitor. Initially I had planned to use my el cheapo desoldering iron to clear out these vias from the back of the board, so that the very close-by capacitor wouldn't matter. Unfortunately, the tip of my desoldering iron is just too wide to clear out an empty via very easily. Instead, I used a 0.6mm semi-conical tip on my Hakko iron and my long-serving $6 plastic spring-loaded desoldering pump, eased along with a couple drops of MG Chem liquid flux. This technique has me heat one side of the via with the iron and after a few seconds to melt the solder, releasing the suction pump to clear out the hole. Easy peasy. Unfortunately, that little cap is kind of in the way. Fortunately, when Atari assembled the board the caps used have a little bit longer legs than strictly necessary. You can actually use a small screwdriver to push the cap to the side and gain better access to the top of the via with the soldering iron without burning or melting the plastic, so that's what I did. Once the cap was pushed aside by a millimeter or two, clearing it out with the tiny tip on my iron was a piece of cake.

Another thing of note - unlike my last U1MB, a little over two years ago, this time Lotharek included a four-wire connector with plenty of fine-gauge wire pre-installed for the jumpers to the board. This makes installation much easier for the part-time hobbyist who may not like to keep rarely-used tools and connectors around, or spend the money to buy them for a single job. So thumbs up to Lotharek for this little helpful touch.

Once I'd verified that the board would boot and was functionally stable, I removed the jumper connector, secured the four wires together with a small zip tie, then twisted them into a tight bundle and tucked them neatly up and around the U1MB before plugging the connector back in. The board is mounted in one of the now-vacant holes from the RF shielding, With the mounting rod screwed down tightly on the support posts using two of the included nuts, and the MMU cable folded and routed underneath, it sits very securely at the back of the machine next to the AC rectifier.

Two years ago I had tried to mount my first Ultimate 1MB into another 1200XL but the combo in that machine was never stable - the real-time clock kept resetting, sometimes the board graphics and text were corrupted and the computer would lock up. That same U1MB went instead into an 800XL and has been completely perfect there for two-plus years now. I never figured out why that U1MB wouldn't run well in that machine but based on that experience, this time I decided to do some stability tests before I trust it. After it booted up yesterday, I tried a number of cartridges, with and without SDX enabled, I reset and rebooted the computer multiple times, and let it run for over 4 hours without issue. Today I put my SIDE2 cartridge into it, ran programs off the CF card hard drive, saved and loaded files and let it run for about 4 hours again, also without issue. (*)

​So I powered it down, cleaned up the board, reassembled the computer, and flashed Jon's latest-release BIOS, SIDE Loader, and PBI BIOS, then I updated SDX, configured my OS and BASIC slots as I prefer them, and voila! The machine has run all day and it's been rock-solid.

So until I get the urge to put an internal CF card IDE hard drive solution into the machine, or maybe a stereo POKEY board or something, this one is done and ready for daily use at long last. Huzzah.

Here's where the Reset line is connected, right above that little capacitor I mentioned:

All four wires: Phi2, Reset, R/W and Halt:

Assembly more or less done, ready to test:

Ta da, it works!

Flashed with Jon's latest firmware, and ready for duty:

(*) Hat-tip and thanks to Jon, again, for his tip about the SIDE2 cartridge in the 1200XL; at his suggestion, I used fine-grit sandpaper to sand off about half a millimeter from each side of the SIDE2 cartridge case and now the cartridge fits into the 1200XL cartridge tunnel perfectly. You still don't have the same ease of access to the sliding switch on the front of the cartridge but the cartridge itself slides in and out easily, with no changes required to the 1200XL cartridge tunnel at all.

Did you install the UAV in both 1200XLs. I did a SV 2.1 on mine and the video is so good I don't believe the UAV would make it any better. I would like to know if anyone has done the UAV and SV2.1 so they could compare.

Did you install the UAV in both 1200XLs. I did a SV 2.1 on mine and the video is so good I don't believe the UAV would make it any better. I would like to know if anyone has done the UAV and SV2.1 so they could compare.

I did a UAV on both machines, an older Rev C on the "Ugly Duckling" that's the object of most of this thread, and a Rev D on a second 1200XL. They both look fantastic. I just can't imagine a discrete-component replacement-type mod can possibly look as good as intercepting the signals right off the chip and running them through a custom-designed board with carefully-specified modern components designed to produce as 'scope-perfect a video output signal as possible.

Of course, every machine is different after 30 - 40 years and your mileage may vary, but the UAV is just so easy to install and produces such a great signal it's a no brainer to me.